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https://issues.apache.org/jira/browse/ZOOKEEPER-2247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15131644#comment-15131644
]
Rakesh R commented on ZOOKEEPER-2247:
-------------------------------------
Thanks [~fpj] for the comments.
bq. Can we please use 30s by default?
Agreed.
bq. Shouldn't it be while (zk.isRunning()) instead?
{code}
public boolean isRunning() {
return state == State.RUNNING || state == State.ERROR;
}
public boolean isStateRunning() {
return state == State.RUNNING;
}
{code}
State transitions:
1. At the beginning the state will be {{INITIAL}}.
2. After the successful start, update the server state to {{RUNNING}}
3. When there is an internal error, update the server state to {{ERROR}}.
4. On shutdown, update the server state to {{SHUTDOWN}}
Standlone server watch logic:
The newly added watch logic will periodically checks {{RUNNING}} state and come
out of the loop if it sees a state other than {{RUNNING}}. With
{{zks.isRunning()}} method, it will return true if server is {{RUNNING}} or
{{ERROR}} state. So if I use {{isRunning()}}, it will never come out of the
loop on error situations, right?
bq. For the leader and learner, why is it isStateRunning here:
Here also the same case. It should come out of the {{readPacket}} function if
the server is not RUNNING. With {{zks.isRunning()}}, it will never identify the
{{ERROR}} state and continue reading packet, right?
{{isRunning}} method is reflecting dual state, {{running}} as well as {{running
with an error}}, I think that causes the confusion. I failed to find a better
name for this function.
> Zookeeper service becomes unavailable when leader fails to write transaction
> log
> --------------------------------------------------------------------------------
>
> Key: ZOOKEEPER-2247
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2247
> Project: ZooKeeper
> Issue Type: Bug
> Affects Versions: 3.5.0
> Reporter: Arshad Mohammad
> Assignee: Arshad Mohammad
> Priority: Critical
> Fix For: 3.4.9, 3.5.2, 3.6.0
>
> Attachments: ZOOKEEPER-2247-01.patch, ZOOKEEPER-2247-02.patch,
> ZOOKEEPER-2247-03.patch, ZOOKEEPER-2247-04.patch, ZOOKEEPER-2247-05.patch,
> ZOOKEEPER-2247-06.patch, ZOOKEEPER-2247-07.patch, ZOOKEEPER-2247-09.patch,
> ZOOKEEPER-2247-10.patch, ZOOKEEPER-2247-11.patch, ZOOKEEPER-2247-12.patch,
> ZOOKEEPER-2247-b3.5.patch
>
>
> Zookeeper service becomes unavailable when leader fails to write transaction
> log. Bellow are the exceptions
> {code}
> 2015-08-14 15:41:18,556 [myid:100] - ERROR
> [SyncThread:100:ZooKeeperCriticalThread@48] - Severe unrecoverable error,
> from thread : SyncThread:100
> java.io.IOException: Input/output error
> at sun.nio.ch.FileDispatcherImpl.force0(Native Method)
> at sun.nio.ch.FileDispatcherImpl.force(FileDispatcherImpl.java:76)
> at sun.nio.ch.FileChannelImpl.force(FileChannelImpl.java:376)
> at
> org.apache.zookeeper.server.persistence.FileTxnLog.commit(FileTxnLog.java:331)
> at
> org.apache.zookeeper.server.persistence.FileTxnSnapLog.commit(FileTxnSnapLog.java:380)
> at org.apache.zookeeper.server.ZKDatabase.commit(ZKDatabase.java:563)
> at
> org.apache.zookeeper.server.SyncRequestProcessor.flush(SyncRequestProcessor.java:178)
> at
> org.apache.zookeeper.server.SyncRequestProcessor.run(SyncRequestProcessor.java:113)
> 2015-08-14 15:41:18,559 [myid:100] - INFO
> [SyncThread:100:ZooKeeperServer$ZooKeeperServerListenerImpl@500] - Thread
> SyncThread:100 exits, error code 1
> 2015-08-14 15:41:18,559 [myid:100] - INFO
> [SyncThread:100:ZooKeeperServer@523] - shutting down
> 2015-08-14 15:41:18,560 [myid:100] - INFO
> [SyncThread:100:SessionTrackerImpl@232] - Shutting down
> 2015-08-14 15:41:18,560 [myid:100] - INFO
> [SyncThread:100:LeaderRequestProcessor@77] - Shutting down
> 2015-08-14 15:41:18,560 [myid:100] - INFO
> [SyncThread:100:PrepRequestProcessor@1035] - Shutting down
> 2015-08-14 15:41:18,560 [myid:100] - INFO
> [SyncThread:100:ProposalRequestProcessor@88] - Shutting down
> 2015-08-14 15:41:18,561 [myid:100] - INFO
> [SyncThread:100:CommitProcessor@356] - Shutting down
> 2015-08-14 15:41:18,561 [myid:100] - INFO
> [CommitProcessor:100:CommitProcessor@191] - CommitProcessor exited loop!
> 2015-08-14 15:41:18,562 [myid:100] - INFO
> [SyncThread:100:Leader$ToBeAppliedRequestProcessor@915] - Shutting down
> 2015-08-14 15:41:18,562 [myid:100] - INFO
> [SyncThread:100:FinalRequestProcessor@646] - shutdown of request processor
> complete
> 2015-08-14 15:41:18,562 [myid:100] - INFO
> [SyncThread:100:SyncRequestProcessor@191] - Shutting down
> 2015-08-14 15:41:18,563 [myid:100] - INFO [ProcessThread(sid:100
> cport:-1)::PrepRequestProcessor@159] - PrepRequestProcessor exited loop!
> {code}
> After this exception Leader server still remains leader. After this non
> recoverable exception the leader should go down and let other followers
> become leader.
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